Genetics PP9 (Chapter 5 Second Half)

Dilutes dilute allele reduces amount of pigment in

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Unformatted text preview: or --> s E.g. grey cat is dilute black, cream is dilute E.g. orange orange D_ dd D_ dd C. Modifier Genes C. 1. Dilutes s E.g. horse -- diluting Ccr allele x only affects pheomelanin (red pigment) x has incomplete dominance red pigment + CC = chestnut red red pigment + CCcr = palomino red red pigment + CcrCcr = cremello red ee CCcr ee CC ee CcrCcr VI. Interactions Between Genes C. Modifier Genes 2. Superimposing genes 2. Don’t affect ratios s E.g. Spotting alleles prevent pigments from E.g. reaching some hairs -- affects any color reaching x Tobiano Tobiano allele is a simple dominant dihybrid ratio dihybrid X Toto Ee Toto Ee 9 Toto Ee 3 Toto ee 3 toto Ee 1 toto ee VI. Interactions Between Genes C. Modifier Genes 2. Superimposing genes 2. s E.g. Spotting alleles xS allele has incomplete dominance -allele SS has more white than Ss SS Present in most mammals but rare in the Present wild wild Ss SS VII. Environmental Influences VII. s Happens at some level with all genes A. Sex-influenced and sex-limited traits A. x E.g. Goat beards B. Temperature-sensitive traits x E.g. Himalayan rabbits and cats Reared below 20 C Reared above 30 C Temperature controls expression of vestigal wing mutation VIII. Multiple Alleles Versus Multiple Genes s How do you tell if a new phenotype is due to new How allele or new gene interaction? allele x A. A. For recessive mutations, determine by using complementation test complementation 2 different mutant lines have same phenotype different Cross parents that are each homozygous for one of the mutations one a b a b a a+ b a p. 113 b+ b+ a+ b a b a b a b Mutant a b+ a+ b a b+ a+ b a a+ p. 113 b+ b Wildtype VIII. Multiple Alleles of One Gene VIII. A. For recessive mutations, determine by using complementation test complementation x B. B. For dominant mutations, must analyze multiple crosses multiple Spotting due to same or different genes? To _ ov ov to to Ov ov IX. Continuous Traits IX. A. Pleiotropy Single gene affects multiple traits s E.g. White eye (w) mutation in Drosophila E.g. Drosophila also affects “kidney” function “kidney” s E.g. Lethal white foal disease (Ov Ov) E.g. causes white coat and defective digestive and system system IX. Continuous Traits IX. A. Pleiotropy B. Polygenic trait B. Single trait is affected by multiple genes Single x Standard for most phenotypic traits x Leads to continuum of phenotypes s E.g. Eye color in Drosophila controlled by E.g. Drosophila about 100 different genes about s E.g. Human height s X. Cytoplasmic Inheritance X. s Phenotype of offspring determined by genes Phenotype genes inherited exclusively from mother exclusively A. Maternal Inheritance -- Organelles A. 1. Usually inherited only from mother 1. 2. Mitochondria and choloroplasts contain 2. small chromosomes small 3. Traits due to organellar genes can vary 3. from cell to cell from X. Cytoplasmic Inheritance X. s Phenotype of offspring determined by genes Phenotype genes inherited only from mother inherited A. Maternal Inheritance -- Organelles A. 1. Usually inherited only from mother 1. 2. Mitochondria and choloroplasts contain 2. small chromosomes small 3. Traits can vary from cell to cell x Sorting can happen during cell division s E.g. Leaf color of four o’clock plants Only the mother plant matters in determining offspring phenotype X. Cytoplasmic Inheritance X. B. Maternal Effects B. s Phenotype of offspring determined by products Phenotype products (usually mRNAs) from mother’s genes (usually s E.g. Shell coiling in Limnaea XI. Genomic Imprinting XI. s Sex of parent determines whether an allele is Sex active or inactive in offspring active x Complete imprint is relatively rare Partial imprinting more common x Feature of individual gene Most common for genes on X chrm x Some genes are mother-active, others are Some father-active father-active Paternal Imprinting XI.Genomic Imprinting XI.Genomic s Sex of parent determines whether an allele Sex is active or inactive in offspring is s E.g. Igf2 protein affects fetal growth...
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This note was uploaded on 09/27/2013 for the course BIO 342 taught by Professor Susanhoffman during the Fall '13 term at Miami University.

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